Author ORCID Identifier
0000-0003-0616-8536
Document Type
Dissertation
Date of Award
8-31-2022
Degree Name
Doctor of Philosophy in Environmental Engineering - (Ph.D.)
Department
Civil and Environmental Engineering
First Advisor
Michel Boufadel
Second Advisor
Taha F. Marhaba
Third Advisor
William Pennock
Fourth Advisor
Lucia Rodriguez-Freire
Fifth Advisor
Kenneth Lee
Abstract
Spilled oil slicks are likely to break into droplets offshore due to wave energy. The fate and transport of such droplets are affected by suspended particles in local marine environment, through forming oil particle aggregates (OPAs). OPA formation is affected by various factors, including the properties of the particles and oil, the mixing energy and duration, etc. To investigate the impact of these factors, lab scale experiments are conducted by using seawater (both artificial and natural) and kaolinite and silica to simulate the formation of OPAs in baffled flasks. In the first experiment, 9 gm and 3 gm spherical silica are used, plus the pure kaolinite and those modified by removing the hydroxyl groups to increase its hydrophobicity. The concentration ratio of particles to crude oil is also changed in three levels. In the second experiment, three oils at different viscosity are chosen (fresh ANS (Alaska North Slope), weathered ANS (10% mass loss) and a dilbit AWB (Access Western Blend)) to understand the impact of oil properties on the OPA formation. The third experiment is to investigate the impact of the mixing energy, and the mixing time, to see the mechanical changes of formed OPAs. Furthermore, natural sediments and seawater are collected from New Jersey shore to further understand the formation of OPAs on the fate of dispersed oils (biodegradation happens).
Experiment #1 fmds that the distribution of particles on the oil droplet is more uniform with the 9 gm silica particles. The OPAs of the 3 gm silica particles are much smaller than those of the 9 gm particles. For kaolinite particles that are elongated-sheeted of length around 10 gm, it is found that increasing the hydrophobicity of the particles from a contact angle (CA) of ~ 29° to 38°, increases the penetration of the particles in the oil through a projectile penetration mechanism. For an oil concentration of 500 mg/L, a particle concentration of 100 mg/L is incapable of fragmenting the oil droplets, but particle concentration of 500 mg/L fragments the droplets similarly to a concentration of 1500 mg/L. The viscosity is found able to affect the efficiency of OPA formation in Experiment #2. The light to medium viscous oils show similar droplet size distribution (DSD) after interacting with particles, and the trapping efficiency is at the same level; while highly viscous oil forms OPA in lower efficiency, but the interaction is stronger.
Two mixing energies (energy dissipation rates of 0.05 and 0.5 watt/kg) and four durations (10 min, 30 min, 3 h, and 24 h) are considered in Experiment #3. Results indicate that the negatively buoyant OPAs formed with original kaolinite at low mixing energy reaggregate after 24 hours. At higher mixing energy, the OPAs form within 10 min and the formation reaches equilibrium at 3 h by original kaolinite. For modified kaolinite, the OPAs continue to form through 24 h. When natural sediments and sweater are used in Experiment #4, the results show that the interaction between oil droplets and the intertidal sediments is not stable compared with the oil interaction with the subtidal sediments. However, the adsorption of oil on subtidal sediments prevents the degradation of crude oil as the total weight loss is 25%, similar to that by intertidal sediments. The elongated-sheeted kaolinite penetrates the oil droplets during OPA formation, and major degradation in this type OPA results to a total 51% oil weight loss.
Recommended Citation
Ji, Wen, "Formation of oil particle aggregates and the impact on the fate of oil" (2022). Dissertations. 1847.
https://digitalcommons.njit.edu/dissertations/1847
